Neutral and cationic (η6-arene)-ruthenium(II) complexes containing the iminophosphorane–phosphine ligand Ph2PCH2P(N-p-C5F4N)Ph2: influence of the arene ring in catalytic transfer hydrogenation of cyclohexanone

Ruthenium(II) dimers [{Ru(η6-arene)(μ-Cl)Cl}2] (1a–f) readily react with the iminophosphorane–phosphine ligand Ph2PCH2P(N-p-C5F4N)Ph2 (2), in dichloromethane at room temperature, to afford the neutral derivatives [Ru(η6-arene)Cl2{k1-P-Ph2PCH2P(N-p-C5F4N)Ph2}] (arene=C6H6 (3a), 1-iPr-4-C6H4Me (3b), 1,3,5-C6H3Me3 (3c), 1,2,3,4-C6H2Me4 (3d), 1,2,4,5-C6H2Me4 (3e), C6Me6 (3f)). Treatment of 3a–f with AgSbF6 in dichloromethane yields the cationic species [Ru(η6-arene)Cl{k2-P,N-Ph2PCH2P(N-p-C5F4N)Ph2}][SbF6] (4a–f). The catalytic activity of complexes 3 and 4 in transfer hydrogenation of cyclohexanone by propan-2-ol has been studied. Among them, the cationic derivative [Ru(η6-C6Me6)Cl{k2-P,N-Ph2PCH2P(N-p-C5F4N)Ph2}][SbF6] (4f) shows the highest activity. Electrochemical data for 3 and 4 are also reported.